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Ch. 8 - Magnetism
Ch. 8 - Magnetism
SPS10. Students will investigate the properties of electricity and magnetism.
b. Explain the flow of electrons in terms of alternating and direct current.
c. Investigate applications of magnetism and/or its relationship to the movement of electrical charge as it relates to electromagnets, simple
motors, permanent magnets
Ch. 8 - Magnetism
Ch. 8 - Magnetism
I. Characteristics of Magnets Magnetism Magnetic poles Magnetic field Magnetic domain
A. MagnetismMagnetism
force of attraction or repulsion between unlike or like poles
due to the arrangement of electrons
closely related to electricity
B. Magnetic PolesMagnetic Poles
like poles repel
unlike poles attract
a broken magnet creates new poles
C. Magnetic FieldMagnetic Field
area around a magnet where magnetic forces act
field lines show direction of field (NS)
D. Magnetic DomainMagnetic Domain
groups of atoms with aligned magnetic poles
in a magnetized object, domains are all aligned
domain
Ch. 22 - Magnetism
Ch. 22 - Magnetism
II. Uses of Magnetic Fields Electromagnet Speaker Motor
A. ElectromagnetElectromagnet
strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core
acts like a bar magnet when current is on
B. SpeakerSpeaker
electrical energy mechanical energy
wire coil moves back & forth as its magnetic field interacts with the field of a fixed magnet
forced vibration causes the cone to move sound
C. MotorMotor
electrical energy mechanical energy
electromagnet rotates between the poles of a fixed magnet
commutator reverses the poles of the e’magnet
C. Motor
brushes & wires to battery field magnet
armature & commutatorassembled motor
Ch. 22 - Magnetism
Ch. 22 - Magnetism
III. Producing Electric Current Electromagnetic Induction Electric Generator DC & AC Transformer
A. Electromagnetic InductionElectromagnetic Induction
producing a current by moving a wire through a magnetic field
some microphones work just like mini-speakers in reverse
sound waves cause coil to move current
Dynamic Microphone
Coil
B. Electric GeneratorElectric Generator
mechanical energy electrical energy
armature is rotated between magnet poles
magnetic field induces a current in the wire coil
MOTORGENERATOR
B. Electric Generator Hydroelectric Dam
PE of lake water is converted to KE
mechanical KE turns the generator shaft which creates electrical energy
C. DC & ACDirect Current (DC)
current flows in one direction dry cells
Alternating Current (AC) current reverses its direction
at regular intervals electrical outlets
Video
D. TransformerTransformer
increases or decreases AC voltage primary coil AC produces a magnetic field that
induces AC in the secondary coil voltage ratio = ratio of turns in each coil
D. TransformerStep-up Transformer
increases the voltage more turns power plants
Step-down Transformer decreases the voltage fewer turns household appliances
(hairdryers, etc.)